In current touch sensitive systems, several parameters of a stylus are typically obtained. One can be the pressure experienced at the tip of the stylus; a second can be the tilt angle of the stylus; a third can be the pointing direction of the stylus; and a fourth can be the rotation speed of the stylus. The tilt angle herein refers to an angle of the stylus with respect to the surface of a touch panel or touch screen (the term “touch screen” is used hereinafter to refer to both of these devices). The pointing direction of the stylus refers to a direction projected on the touch screen in which the body of the stylus is pointing towards the tip of the stylus. The rotation speed refers to the angular speed of an axis along the body of the stylus towards the tip of the stylus rotating in a clockwise or anticlockwise direction.
Pressure values can be detected by a pressure sensor on the stylus or a pressure sensor on the touch screen. The pressure sensor can be an active element or a passive element. The applicants has previously proposed methods of employing a passive element on a stylus, especially a pressure sensor employing a force sensing capacitor (FSC) or a force sensing resistor (FSR) configured to detect the pressure experienced by the tip of the stylus. The pressure values detected by the stylus can be transmitted by a wired transmission, a wireless transmission or by emitting electrical signals from the tip of the stylus. Various modulation methods can be used for transmitting the pressure values to a controller or an operating system of the touch sensitive system. The touch controller may also be used to detect a pressure exerted on the touch screen by the stylus via a pressure sensor of the touch screen, such as a FSC or a FSR.
One of the methods for detecting the tilt angle is to let a plurality of electrodes of the stylus transmit electrical signals that are the same or different simultaneously or in a time-multiplexed manner. The touch controller then uses electrodes on the touch screen to detect these electrical signals in order to determine a plurality of proximity/touch locations of these electrodes, which are in proximity or touching the touch screen. Since the plurality of electrodes are disposed at various different locations on the stylus, based on two or more proximity/touch locations, the title angle and the pointing direction of the stylus can be determined. Furthermore, based on changes of the plurality of proximity/touch locations corresponding to the plurality of electrodes, the rotation speed of the stylus can be calculated.
In addition, an angular accelerometer, a gyroscope or another device for indicating the posture of the stylus can also be provided on both the stylus and the touch controller. By comparing two postures, the relative pointing direction of the stylus with respect to the touch screen can be known. Moreover, when the touch controller detects a stylus on the touch screen, and when the pressure value at the tip of the stylus is greater than zero, the tile angle of the stylus can also be determined. With the angular accelerometer or gyroscope provided on the stylus, the above rotation speed can also be directly determined.
As described before, there are several ways for determining the aforementioned parameters; however, the present invention does not limit which particular method is used for determining these parameters, nor does it limit the way in which these parameters are transmitted to the touch controller and/or a main processor or operating system belonging to the touch controller. Once the operating system or an application program has determined the aforementioned four parameters, some or all parameters associated with display contents of the screen can be individually or jointly adjusted. These display contents may include brush strokes, that is, parameters such as the shade and brightness of the color, and the size, breadth and shape of a coloring range can be adjusted.
Since a user needs to hold a stylus in order to control the brush strokes of the stylus, he/she might be sensitive to the pressure at the tip of the stylus. In some cases, in order to ensure the correct input of the pressure values, the user may have to hold the stylus vertically to the touch screen. However, holding the stylus in such a posture for a long period of time is strenuous; it also renders some parameters of the stylus inaccessible. For example, if the tilt angle is zero, that is, the stylus is vertical to the touch screen, then it is impossible to determine the pointing direction of the stylus, and it also makes it difficult to determine the rotation speed of the stylus.
In view of this, a method for calibrating the pressure at the tip of the stylus is urgently in need in order to allow a user to better control the pressure while being able to comfortably hold the stylus at an angle.
Moreover, when a user is using a stylus, if a palm rejection area can be set up according to the habit of the user, error operations caused by the palm can be effectively reduced. Meanwhile, there is a need for reducing the palm rejection area, so that the touch screen can receive touch sensitive commands in other areas than the palm rejection area. In the case of several hands simultaneously operating on a big touch screen, there is a need for setting up an individual palm rejection area for each hand, regardless of whether the hands are right or left hands.